Development in one domain may have profound effects on developmental progress in other domains. This research examines how very young children's learning their first noun categories -categories such as house, chair, dog, and spoon - may play a formational role in organizing processes of visual object recognition, and how in turn these processes may feedback onto and influence the nature and speed and of early lexical learning. Further, the work examines the relation between these developmental achievements and symbolic play. Symbolic play has been used as am important marker of language delay but the mechanistic nature of the link between symbolic play and early language development has not been understood. This proposed research tests the idea that the link is through the effects of lexical learning on visual object recognition. The experiments include studies of typically developing children from 15 to five years of age and also studies of children (so-called late talkers) whose progress in early word learning is (at least initially) slower than their peers and who often (even after seeming to catch up in language) show learning deficits in school. The studies include observational studies, experimental studies directed to detailing the specific cognitive processes involved in lexical learning and object recognition, and training studies that seek to understand the causal mechanisms of change by experimentally inducing change in the laboratory. [unreadable] [unreadable] [unreadable]